Conventionally, there is known a double-sided engagement type fabric surface fastener, in which hook-like engagement elements exist on a top surface of a base fabric, and loop-like engagement elements exist on a bottom surface of the base fabric. As compared with a conventional surface fastener, which is manufactured by attaching two types of surface fasteners respectively provided with hook-like engagement elements and loop-like engagement elements on surfaces thereof, to both surfaces of a support base fabric, the double-sided engagement type fabric surface fastener is constituted of one type of surface fasteners. Therefore, in recent years, a demand for the double-sided engagement type fabric surface fastener has been increasing.
In the double-sided engagement type fabric surface fastener, it is very important to fix the engagement elements to a base fabric so that the engagement elements are not pulled out of the base fabric. For instance, as a representative example, Patent Literature 1 describes a surface fastener provided with engagement elements on both surfaces thereof, wherein the engagement elements are fixed to a base fabric by coating, on the surface fastener, liquid or emulsion liquid containing polyurethane resin, acrylic resin, ASB resin, SB resin, polyester resin, silicon resin, or the like by an airless spray method.
Patent Literature 2 describes a surface fastener provided with engagement elements on both surfaces thereof, wherein the engagement elements are fixed to a base fabric, with use of a hot melt adhesive in the form of powders and containing ethylene vinyl acetate, polyethylene, atactic polypropylene, ethylene-acrylic acid, copolyamide, copolyester, or the like.
Patent Literature 3 describes a surface fastener provided with engagement elements on both surfaces thereof, wherein the engagement elements are fixed to a base fabric with use of a thermal adhesive yarn as a part of a ground warp yarn, or heat melt resin powder having a low melting point.
Patent Literature 4 describes a double woven cloth constituted of a top base fabric and a bottom base fabric, wherein the fabrics are integrally adhered by weaving a yarn for engagement elements, weaving a thermal adhesive yarn having a low melting point, and subjecting the yarns to heat melting.
In the manufacturing methods described in Patent Literature 1 and Patent Literature 2, an adhesive is coated on one of the surfaces of the base fabric of the surface fastener having engagement elements on both surfaces thereof. In other words, an adhesive is coated on the surface having hook-like engagement elements or on the surface having loop-like engagement elements. In this case, if an adhesive is coated on a multifilament yarn constituting loop-like engagement elements, fibers constituting the multifilament yarn are bundled and fixed to a monofilament form by the adhesive. This may result in great loss of engaging performance. Therefore, normally, a method of coating an adhesive on the surface having hook-like engagement elements is employed. Coating an adhesive on a hook-like engagement element surface, however, may naturally cause adhesion of adhesive to the surface of a yarn for hook-like engagement elements.
A hook-like engagement element is formed into a hook shape by forming a monofilament yarn into a loop shape, and cutting a leg portion of the loop into a hook shape. The process of cutting leg portions of monofilament loops is carried out after fixing a yarn for engagement elements to a base fabric by an adhesive or the like. Specifically, in the manufacturing methods in Patent Literature 1 and Patent Literature 2, hook-like engagement elements are formed by cutting loops of a monofilament yarn to which an adhesive is adhered. In the process of cutting a monofilament yarn to which an adhesive is adhered, a cutting blade may peel off a part of the adhesive adhered to the monofilament yarn. Partly peeled-off adhesive may remain on the hook-like engagement elements, and it looks like dust fell on the hook-like engagement elements. This may impair the external appearance. If the amount of adhesive to be coated is reduced in an attempt to suppress deterioration of the external appearance, the engagement elements are likely to be pulled out of the base fabric by repeated engagement and disengagement. This may greatly lower the durability.
Further, in the techniques described in Patent Literature 3 and Patent Literature 4, a thermal adhesive yarn is used as a part of a ground warp yarn. When yarns of different properties are used as a ground warp yarn, crease may be generated on a surface fastener because of different heat shrinkage rates between the yarns. If the dyeing properties differ between the yarns, streaks of uneven colors may appear. This may impair the external appearance. Further, if a thermal adhesive yarn is used as a ground warp yarn, a yarn for engagement elements that is woven in parallel to a ground warp yarn may not be securely fixed to the base fabric, and the engagement elements are likely to be pulled out of the base fabric by engagement and disengagement. This may deteriorate the durability.
The present inventors have found that in a double-sided engagement type fabric surface fastener having hook-like engagement elements and loop-like engagement elements respectively on a top surface and a bottom surface of a base fabric, use of a thermal adhesive yarn as a ground weft yarn eliminates the need of coating an adhesive on the base fabric, and eliminates the need of using a thermal adhesive yarn as a ground warp yarn. This makes it possible to obtain a double-sided engagement type fabric surface fastener having good durability, engaging strength, and external appearance.
Conventionally, nylon fibers are dedicatedly used as a material for a surface fastener. It is known that when nylon fibers are used as a material for hook-like engagement elements, loop-like engagement elements, a ground warp yarn, or a ground weft yarn, wet dimensional stability may be deteriorated, and the surface fastener may have a wavy appearance by absorbing water.
Further, in a conventional surface fastener, resistance against pulling out of engagement elements is obtained by coating an adhesive on a base fabric, so that hook-like engagement elements and loop-like engagement elements are not pulled out of the base fabric by engagement and disengagement. When an adhesive is coated on a base fabric, the base fabric becomes rigid because the base fabric is hardened by the adhesive. A rigid base fabric is not favorable in the garment field where softness is required.
There is reported a technique such that thermal adhesive fibers are used as fibers constituting a surface fastener, and fibers for engagement elements in a base fabric are adhered by melting the thermal adhesive fibers in order to enhance the resistance against pulling out of engagement elements (see Patent Literature 5). When polyamide fibers are used as fibers constituting a base fabric, however, the fiber performance may be greatly deteriorated by thermal adhesion treatment, because the polyamide fibers have a poor heat resistance.